The present invention relates to a method of isolating soluble fiber from cereal grains. In particular, the invention is directed to an efficient method for producing high quality beta glucan isolates for use as food additives, dietary supplements, seasonings, ingredients, food intermediates and food products which are ready to eat or may undergo a further processing step.
High fiber products are generally considered to be healthful foods and food ingredients. Foods high in water insoluble fiber are known to improve regularity and bulk formation. Water-soluble fiber content in natural and processed foods has been linked to such beneficial effects as cholesterol reduction, blood sugar regulation in diabetics and prevention of colon cancer. Yet it is widely recognized that soluble fiber is lacking in the diet of most populations, which may be due in part to the taste, availability and difficulty in obtaining high fiber sources. Accordingly there have been significant research and development efforts in the food industry to create high fiber, multifunctional food additives, supplements, ingredients for use in the manufacture of processed foods and food intermediates for health conscious consumers.
Cholesterol in humans comes from primarily two sources, the bodies own production of cholesterol (endogenic) and dietary cholesterol. Typically, the average person consumes between 350-400 milligrams of cholesterol daily, while the recommended intake is around 300 milligrams. Increased dietary cholesterol consumption, especially in conjunction with a diet high in saturated fat intake, can result in elevated serum cholesterol. Elevated serum cholesterol is a well-established risk factor for heart disease and therefore there is a need to mitigate the undesired effects of cholesterol accumulation. High cholesterol levels are generally considered to be those total cholesterol levels at 200 milligrams and above or LDL cholesterol levels at 130 milligrams and above.
Lipoproteins contain specific proteins and varying amounts of cholesterol, triglycerides and phospholipids. There are three major classes of lipoproteins and they include very low-density lipoproteins (xe2x80x9cVLDLxe2x80x9d), low-density lipoproteins (xe2x80x9cLDLxe2x80x9d) and high-density lipoproteins (xe2x80x9cHDLxe2x80x9d). The LDLs are believed to carry about 60-70% of the serum cholesterol present in an average adult. The HDLs carry around 20-30% of serum cholesterol with the VLDL having around 1-10% of the cholesterol in the serum. To calculate the level of non-HDL cholesterol present (find the level of LDL or VLDL levels), which indicates risk, the HDL is subtracted from the total cholesterol value. By lowering the total system LDL cholesterol level, it is believed that certain health risks, such as coronary disease and possibly some cancers, that are typically associated with high cholesterol levels, can be reduced.
Soluble fiber typically remains undigested, except by colonic microflora present in the lower intestines. Soluble dietary fiber is believed to have a beneficial effect in the reduction of high serum cholesterol levels and reducing the risk associated with such elevated levels. In addition, soluble dietary fiber can have the additional beneficial effect of reduced constipation and improved stool regularity. However, too much fiber in the diet can create undesirable gastrointestinal side effects such as flatulence, diarrhea, and abdominal cramps, etc. leading consumers to stay away from food products that contain too much dietary fiber, regardless of any associated health benefits. While some consumers may not completely avoid such products, they also do not typically regularly use such products due to the problems enumerated above or alternatively, or in combination due to the unpleasant taste of such products. This illustrates some of the problems with prior solutions that were aimed at providing high fiber diets directed at lowering cholesterol levels, and highlights the need to create a more balanced solution that fits not only within more normal dietary patterns but also meets consumer demand for better tasting, healthy products.
A principal component of cereal grain-derived soluble fiber is beta-glucan. Beta glucan is a naturally occurring polysaccharide component of cell walls of cereal grains. Beta glucan from cereal grains comprises a family of linear polysaccharides comprising D-glucopyranosyl units and having molecular weights ranging from 5xc3x97105 to 3xc3x97106 Daltons (xe2x80x9cDaxe2x80x9d). The highest concentrations of beta glucan are found in barley and oats, but beta glucan can also be isolated from wheat and corn. It is, as well, a component of yeasts and fungi. As a natural cereal fiber, beta glucan has been incorporated in a variety of processed food by its existence in the cereal grains, however, the level of beta glucan has been relatively minimal.
The demand for high fiber foods by heath conscious consumers has focused the efforts of food scientists to meet the need for sources of high quality beta glucan products. That need is met by the present invention, which provides an efficient method for extracting beta glucans from cereal sources. More particularly, the present invention provides an efficient method of extracting beta glucans from cereal brans to provide food additive compositions having high beta glucan content.
In one embodiment of the present invention, soluble fiber comprising beta glucan is extracted from cereal bran in a process comprising high pressure homogenization of slurries of grain material, preferably cereal bran, in about 4 to about 8 parts per weight water and acid/enzyme-mediated viscosity reduction of the resulting aqueous extract. Viscosity reduction enables high efficiency separation of the beta glucan containing solution from water insoluble bran components. The aqueous extracts can be dehydrated/dried to a concentrate or powder form for subsequent use as a food additive, ingredient, supplement or food intermediate or for formulating dietary supplements in the form of capsules, tablets or water dispersible powders. In one aspect of the invention, at least a portion of co-extracted protein components are denatured/precipitated and separated before dehydration of the aqueous extracts. In one particular embodiment the resulting aqueous extracts are subjected to further bioprocessing comprising enzymatic digestion and yeast culture beneficiation to reduce levels of non-beta glucan components prior to isolation of the beta glucan product. The isolated products typically contain greater than 50% d.s. beta glucan, optimally greater than 70% d.s. beta glucan and less than 10% protein/starches. The process can be carried out in batch or continuous mode.
A still further embodiment of the present invention describes a process for isolating soluble fiber, specifically beta glucan from grain. The process comprises initially forming an aqueous slurry of a comminuted grain material. The slurry comprises water insoluble components of the grain material, which are suspended in an aqueous solution. The aqueous solution comprises water-soluble fiber and protein components of the grain material. Next, the aqueous slurry is acidified. Then an enzyme preparation is added. The enzyme preparation is selected from the group consisting of cellulase, hemicellulase, xylanase and pentosanase in an amount effective to hydrolyze at least a portion of the soluble components and thereby reduce the viscosity of the solution. Next, the water is separated from the insoluble components and from the aqueous solution. The solution is then heated to denature at least a portion of the soluble protein components in order to form a precipitate and a beta glucan product solution that contains beta glucan and non-beta glucan components. Then removing at least a portion of the water from the resulting product solution.
A still further embodiment of the present invention comprises a process for isolating soluble fiber, namely beta glucan from grain, the process comprising the steps of initially forming an aqueous slurry of a comminuted grain material. The slurry contains water insoluble components of the grain material suspended in an aqueous solution. The aqueous solution contains water-soluble fiber and protein components of the grain material. The aqueous slurry is acidified and then an enzyme capable of hydrolyzing at least a portion of the soluble polysaccharide components and reducing the viscosity of the slurry is added. The pH of the slurry is adjusted to about 4.2 and water insoluble components are separated from the aqueous solution. The aqueous solution is heated to denature at least a portion of the soluble protein components. Then the denatured protein components are separated from the aqueous solution to form a beta glucan product solution containing beta glucan and non-beta glucan components. At least a portion of the water from the product solution is then removed.
A yet still further embodiment of the present invention includes a process for isolating soluble fiber comprising beta glucan from grain. The process comprises the steps of, first forming an aqueous slurry of a comminuted grain material. The slurry comprises water insoluble components of the grain material suspended in an aqueous solution that comprises water-soluble fiber and protein components of the grain material. The aqueous slurry is then acidified to a pH of about 3.8 to about 5.5. Then an enzyme preparation is added in an amount effective to hydrolyze at least a portion of the soluble components and thereby reduce solution viscosity. The water insoluble components are then separated from the aqueous solution. Next, the aqueous solution is heated to denature at least a portion of the soluble protein components. Then the denatured protein components are separated from the aqueous solution to form a beta glucan product solution containing beta glucan and non-beta glucan components and finally, removing at least a portion of the water from the product solution.
Additional embodiments of the present invention relate to a product which is created in a powder form and achieved by one of the foregoing process embodiments. Such a product may also be a food ingredient, food supplement or food additive. In addition, a food product or food intermediate is created which has as a component beta glucan obtained in accordance with one of the preferred process embodiments of the present invention.